Abstract
BackgroundA systematic review and meta-analysis of published studies on developmental fluoride neurotoxicity support the hypothesis that exposure to elevated concentrations of fluoride in water is neurotoxic during development. MethodsWe carried out a pilot study of 51 first-grade children in southern Sichuan, China, using the fluoride concentration in morning urine after an exposure-free night; fluoride in well-water source; and dental fluorosis status as indices of past fluoride exposure. We administered a battery of age-appropriate, relatively culture-independent tests that reflect different functional domains: the Wide Range Assessment of Memory and Learning (WRAML), Wechsler Intelligence Scale for Children-Revised (WISC-IV) digit span and block design; finger tapping and grooved pegboard. Confounder-adjusted associations between exposure indicators and test scores were assessed using multiple regression models. ResultsDental fluorosis score was the exposure indicator that had the strongest association with the outcome deficits, and the WISC-IV digit span subtest appeared to be the most sensitive outcome, where moderate and severe fluorosis was associated with a digit span total score difference of −4.28 (95% CI −8.22, −0.33) and backward score with −2.13 (95% CI −4.24, −0.02). ConclusionsThis pilot study in a community with stable lifetime fluoride exposures supports the notion that fluoride in drinking water may produce developmental neurotoxicity, and that the dose-dependence underlying this relationship needs to be characterized in detail.
Highlights
The developing human brain is much more susceptible to injury caused by toxicants than is the mature brain, and the damage incurred is likely to be of a permanent nature as the major windows of developmental vulnerability occur in utero and during infancy and early childhood (Grandjean and Landrigan, 2006; Rice and Barone, 2000)
Our results showed that the standardized weighted mean difference (SMD) in IQ score between exposed and reference populations across studies that gave the average difference in standard deviations (SDs) was -0.45 (95% confidence interval: -0.56, -0.36)
Sixty percent of the subjects examined had moderate or severe fluorosis. These children were exposed to elevated fluoride concentrations in drinking water
Summary
The developing human brain is much more susceptible to injury caused by toxicants than is the mature brain, and the damage incurred is likely to be of a permanent nature as the major windows of developmental vulnerability occur in utero and during infancy and early childhood (Grandjean and Landrigan, 2006; Rice and Barone, 2000). Cause permanent brain injury at low levels of exposure that would have little or no adverse effect in an adult (Grandjean and Landrigan, 2014). The major sources of human exposure to fluoride are drinking water, food, dental products, and pesticides (NRC 2006). A systematic review and meta-analysis of published studies on developmental fluoride neurotoxicity supports the hypothesis that exposure to elevated concentrations of fluoride in water is neurotoxic during development
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